Diabetes mellitus refers to a group of diseases that affect how your body uses blood sugar (glucose). Glucose is vital to your health because it's an important source of energy for the cells that make up your muscles and tissues. It's also your brain's main source of fuel.
The underlying cause of diabetes varies by type. But, no matter what type of diabetes you have, it can lead to excess sugar in your blood. Too much sugar in your blood can lead to serious health problems.
Chronic diabetes conditions include type 1 diabetes and type 2 diabetes. Potentially reversible diabetes conditions include prediabetes and gestational diabetes. Prediabetes occurs when your blood sugar levels are higher than normal, but not high enough to be classified as diabetes. And prediabetes is often the precursor of diabetes unless appropriate measures are taken to prevent progression. Gestational diabetes occurs during pregnancy but may resolve after the baby is delivered.
Diabetes symptoms vary depending on how much your blood sugar is elevated. Some people, especially those with prediabetes or type 2 diabetes, may sometimes not experience symptoms. In type 1 diabetes, symptoms tend to come on quickly and be more severe.
Some of the signs and symptoms of type 1 diabetes and type 2 diabetes are:
Type 1 diabetes can develop at any age, though it often appears during childhood or adolescence. Type 2 diabetes, the more common type, can develop at any age, though it's more common in people older than 40.
When to see a doctor
If you suspect you or your child may have diabetes. If you notice any possible diabetes symptoms, contact your doctor. The earlier the condition is diagnosed, the sooner treatment can begin.
If you've already been diagnosed with diabetes. After you receive your diagnosis, you'll need close medical follow-up until your blood sugar levels stabilize
To understand diabetes, first you must understand how glucose is normally processed in the body.
How insulin works
Insulin is a hormone that comes from a gland situated behind and below the stomach (pancreas).
The role of glucose
Glucose — a sugar — is a source of energy for the cells that make up muscles and other tissues.
Causes of type 1 diabetes
The exact cause of type 1 diabetes is unknown. What is known is that your immune system — which normally fights harmful bacteria or viruses — attacks and destroys your insulin-producing cells in the pancreas. This leaves you with little or no insulin. Instead of being transported into your cells, sugar builds up in your bloodstream.
Type 1 is thought to be caused by a combination of genetic susceptibility and environmental factors, though exactly what those factors are is still unclear. Weight is not believed to be a factor in type 1 diabetes.
Causes of prediabetes and type 2 diabetes
In prediabetes — which can lead to type 2 diabetes — and in type 2 diabetes, your cells become resistant to the action of insulin, and your pancreas is unable to make enough insulin to overcome this resistance. Instead of moving into your cells where it's needed for energy, sugar builds up in your bloodstream.
Exactly why this happens is uncertain, although it's believed that genetic and environmental factors play a role in the development of type 2 diabetes too. Being overweight is strongly linked to the development of type 2 diabetes, but not everyone with type 2 is overweight.
Causes of gestational diabetes
During pregnancy, the placenta produces hormones to sustain your pregnancy. These hormones make your cells more resistant to insulin.
Normally, your pancreas responds by producing enough extra insulin to overcome this resistance. But sometimes your pancreas can't keep up. When this happens, too little glucose gets into your cells and too much stays in your blood, resulting in gestational diabetes.Risk factors for diabetes depend on the type of diabetes.
Risk factors for type 1 diabetes
Although the exact cause of type 1 diabetes is unknown, factors that may signal an increased risk include:
Risk factors for prediabetes and type 2 diabetes
Researchers don't fully understand why some people develop prediabetes and type 2 diabetes and others don't. It's clear that certain factors increase the risk, however, including:
Risk factors for gestational diabetes
Pregnant women can develop gestational diabetes. Some women are at greater risk than are others. Risk factors for gestational diabetes include:
Long-term complications of diabetes develop gradually. The longer you have diabetes — and the less controlled your blood sugar — the higher the risk of complications. Eventually, diabetes complications may be disabling or even life-threatening. Possible complications include:
Complications of gestational diabetes
Most women who have gestational diabetes deliver healthy babies. However, untreated or uncontrolled blood sugar levels can cause problems for you and your baby.
Complications in your baby can occur as a result of gestational diabetes, including:
Complications in the mother also can occur as a result of gestational diabetes, including:
Complications of prediabetes
Prediabetes may develop into type 2 diabetes.
Type 1 diabetes can't be prevented. However, the same healthy lifestyle choices that help treat prediabetes, type 2 diabetes and gestational diabetes can also help prevent them:
Don't try to lose weight during pregnancy, however. Talk to your doctor about how much weight is healthy for you to gain during pregnancy.
To keep your weight in a healthy range, focus on permanent changes to your eating and exercise habits. Motivate yourself by remembering the benefits of losing weight, such as a healthier heart, more energy and improved self-esteem.
Sometimes medication is an option as well. Oral diabetes drugs such as metformin (Glumetza, Fortamet, others) may reduce the risk of type 2 diabetes — but healthy lifestyle choices remain essential. Have your blood sugar checked at least once a year to check that you haven't developed type 2 diabetes.
Symptoms of type 1 diabetes often appear suddenly and are often the reason for checking blood sugar levels. Because symptoms of other types of diabetes and prediabetes come on more gradually or may not be evident, the American Diabetes Association (ADA) has recommended screening guidelines. The ADA recommends that the following people be screened for diabetes:
Tests for type 1 and type 2 diabetes and prediabetes
Glycated hemoglobin (A1C) test. This blood test, which doesn't require fasting, indicates your average blood sugar level for the past two to three months. It measures the percentage of blood sugar attached to hemoglobin, the oxygen-carrying protein in red blood cells.
The higher your blood sugar levels, the more hemoglobin you'll have with sugar attached. An A1C level of 6.5% or higher on two separate tests indicates that you have diabetes. An A1C between 5.7 and 6.4 % indicates prediabetes. Below 5.7 is considered normal.
If the A1C test results aren't consistent, the test isn't available, or you have certain conditions that can make the A1C test inaccurate — such as if you are pregnant or have an uncommon form of hemoglobin (known as a hemoglobin variant) — your doctor may use the following tests to diagnose diabetes:
A blood sugar level less than 140 mg/dL (7.8 mmol/L) is normal. A reading of more than 200 mg/dL (11.1 mmol/L) after two hours indicates diabetes. A reading between 140 and 199 mg/dL (7.8 mmol/L and 11.0 mmol/L) indicates prediabetes.
If type 1 diabetes is suspected, your urine will be tested to look for the presence of a byproduct produced when muscle and fat tissue are used for energy because the body doesn't have enough insulin to use the available glucose (ketones). Your doctor will also likely run a test to see if you have the destructive immune system cells associated with type 1 diabetes called autoantibodies.
Tests for gestational diabetes
Your doctor will likely evaluate your risk factors for gestational diabetes early in your pregnancy:
Your doctor may use the following screening tests:
Initial glucose challenge test. You'll begin the glucose challenge test by drinking a syrupy glucose solution. One hour later, you'll have a blood test to measure your blood sugar level. A blood sugar level below 140 mg/dL (7.8 mmol/L) is usually considered normal on a glucose challenge test, although this may vary at specific clinics or labs.
If your blood sugar level is higher than normal, it only means you have a higher risk of gestational diabetes. Your doctor will order a follow-up test to determine if you have gestational diabetes.
Follow-up glucose tolerance testing. For the follow-up test, you'll be asked to fast overnight and then have your fasting blood sugar level measured. Then you'll drink another sweet solution — this one containing a higher concentration of glucose — and your blood sugar level will be checked every hour for a period of three hours.
If at least two of the blood sugar readings are higher than the normal values established for each of the three hours of the test, you'll be diagnosed with gestational diabetes.
Depending on what type of diabetes you have, blood sugar monitoring, insulin and oral medications may play a role in your treatment. Eating a healthy diet, maintaining a healthy weight and participating in regular activity also are important factors in managing diabetes.
Treatments for all types of diabetes
An important part of managing diabetes — as well as your overall health — is maintaining a healthy weight through a healthy diet and exercise plan:
Healthy eating. Contrary to popular perception, there's no specific diabetes diet. You'll need to center your diet on more fruits, vegetables, lean proteins and whole grains — foods that are high in nutrition and fiber and low in fat and calories — and cut down on saturated fats, refined carbohydrates and sweets. In fact, it's the best eating plan for the entire family. Sugary foods are OK once in a while, as long as they're counted as part of your meal plan.
Yet, understanding what and how much to eat can be a challenge. A registered dietitian can help you create a meal plan that fits your health goals, food preferences and lifestyle. This will likely include carbohydrate counting, especially if you have type 1 diabetes or use insulin as part of your treatment.
Physical activity. Everyone needs regular aerobic exercise, and people who have diabetes are no exception. Exercise lowers your blood sugar level by moving sugar into your cells, where it's used for energy. Exercise also increases your sensitivity to insulin, which means your body needs less insulin to transport sugar to your cells.
Get your doctor's OK to exercise. Then choose activities you enjoy, such as walking, swimming or biking. What's most important is making physical activity part of your daily routine.
Aim for at least 30 minutes or more of aerobic exercise most days of the week, or at least 150 minutes of moderate physical activity a week. Bouts of activity can be as brief as 10 minutes, three times a day. If you haven't been active for a while, start slowly and build up gradually. It's also a good idea to avoid sitting for too long — aim to get up and move if you've been sitting for more than 30 minutes.
Treatments for type 1 and type 2 diabetes
Treatment for type 1 diabetes involves insulin injections or the use of an insulin pump, frequent blood sugar checks, and carbohydrate counting. Treatment of type 2 diabetes primarily involves lifestyle changes, monitoring of your blood sugar, along with diabetes medications, insulin or both.
Monitoring your blood sugar. Depending on your treatment plan, you may check and record your blood sugar as many as four times a day or more often if you're taking insulin. Careful monitoring is the only way to make sure that your blood sugar level remains within your target range. People with type 2 diabetes who aren't taking insulin generally check their blood sugar much less frequently.
People who receive insulin therapy also may choose to monitor their blood sugar levels with a continuous glucose monitor. Although this technology hasn't yet completely replaced the glucose meter, it can significantly reduce the number of fingersticks necessary to check blood sugar and provide important information about trends in blood sugar levels.
Even with careful management, blood sugar levels can sometimes change unpredictably. With help from your diabetes treatment team, you'll learn how your blood sugar level changes in response to food, physical activity, medications, illness, alcohol, stress — and for women, fluctuations in hormone levels.
In addition to daily blood sugar monitoring, your doctor will likely recommend regular A1C testing to measure your average blood sugar level for the past two to three months.
Compared with repeated daily blood sugar tests, A1C testing better indicates how well your diabetes treatment plan is working overall. An elevated A1C level may signal the need for a change in your oral medication, insulin regimen or meal plan.
Your target A1C goal may vary depending on your age and various other factors, such as other medical conditions you may have. However, for most people with diabetes, the American Diabetes Association recommends an A1C of below 7%. Ask your doctor what your A1C target is.
Insulin. People with type 1 diabetes need insulin therapy to survive. Many people with type 2 diabetes or gestational diabetes also need insulin therapy.
Many types of insulin are available, including short-acting (regular insulin), rapid-acting insulin, long-acting insulin and intermediate options. Depending on your needs, your doctor may prescribe a mixture of insulin types to use throughout the day and night.
Insulin can't be taken orally to lower blood sugar because stomach enzymes interfere with insulin's action. Often insulin is injected using a fine needle and syringe or an insulin pen — a device that looks like a large ink pen.
An insulin pump also may be an option. The pump is a device about the size of a small cellphone worn on the outside of your body. A tube connects the reservoir of insulin to a catheter that's inserted under the skin of your abdomen
A tubeless pump that works wirelessly is also now available. You program an insulin pump to dispense specific amounts of insulin. It can be adjusted to deliver more or less insulin depending on meals, activity level and blood sugar level.
In September 2016, the Food and Drug Administration approved the first artificial pancreas for people with type 1 diabetes who are age 14 and older. A second artificial pancreas was approved in December 2019. Since then systems have been approved for children older than 2 years old.
An artificial pancreas is also called closed-loop insulin delivery. The implanted device links a continuous glucose monitor, which checks blood sugar levels every five minutes, to an insulin pump. The device automatically delivers the correct amount of insulin when the monitor indicates it's needed.
There are more artificial pancreas (closed loop) systems currently in clinical trials.
Oral or other medications. Sometimes other oral or injected medications are prescribed as well. Some diabetes medications stimulate your pancreas to produce and release more insulin. Others inhibit the production and release of glucose from your liver, which means you need less insulin to transport sugar into your cells.
Still others block the action of stomach or intestinal enzymes that break down carbohydrates or make your tissues more sensitive to insulin. Metformin (Glumetza, Fortamet, others) is generally the first medication prescribed for type 2 diabetes.
Another class of medication called SGLT2 inhibitors may be used. They work by preventing the kidneys from reabsorbing sugar into the blood. Instead, the sugar is excreted in the urine.
Transplantation. In some people who have type 1 diabetes, a pancreas transplant may be an option. Islet transplants are being studied as well. With a successful pancreas transplant, you would no longer need insulin therapy.
But transplants aren't always successful — and these procedures pose serious risks. You need a lifetime of immune-suppressing drugs to prevent organ rejection. These drugs can have serious side effects, which is why transplants are usually reserved for people whose diabetes can't be controlled or those who also need a kidney transplant.
Bariatric surgery. Although it is not specifically considered a treatment for type 2 diabetes, people with type 2 diabetes who are obese and have a body mass index higher than 35 may benefit from this type of surgery. People who've undergone gastric bypass have seen significant improvements in their blood sugar levels. However, this procedure's long-term risks and benefits for type 2 diabetes aren't yet known.
Treatment for gestational diabetes
Controlling your blood sugar level is essential to keeping your baby healthy and avoiding complications during delivery. In addition to maintaining a healthy diet and exercising, your treatment plan may include monitoring your blood sugar and, in some cases, using insulin or oral medications.
Your doctor also will monitor your blood sugar level during labor. If your blood sugar rises, your baby may release high levels of insulin — which can lead to low blood sugar right after birth.
Treatment for prediabetes
If you have prediabetes, healthy lifestyle choices can help you bring your blood sugar level back to normal or at least keep it from rising toward the levels seen in type 2 diabetes. Maintaining a healthy weight through exercise and healthy eating can help. Exercising at least 150 minutes a week and losing about 7% of your body weight may prevent or delay type 2 diabetes.
Sometimes medications — such as metformin (Glucophage, Glumetza, others) — also are an option if you're at high risk of diabetes, including when your prediabetes is worsening or if you have cardiovascular disease, fatty liver disease or polycystic ovary syndrome.
In other cases, medications to control cholesterol — statins, in particular — and high blood pressure medications are needed. Your doctor might prescribe low-dose aspirin therapy to help prevent cardiovascular disease if you're at high risk. However, healthy lifestyle choices remain key.
Signs of trouble in any type of diabetes
Because so many factors can affect your blood sugar, problems may sometimes arise that require immediate care, such as:
High blood sugar (hyperglycemia). Your blood sugar level can rise for many reasons, including eating too much, being sick or not taking enough glucose-lowering medication. Check your blood sugar level as directed by your doctor, and watch for signs and symptoms of high blood sugar — frequent urination, increased thirst, dry mouth, blurred vision, fatigue and nausea. If you have hyperglycemia, you'll need to adjust your meal plan, medications or both.
Increased ketones in your urine (diabetic ketoacidosis). If your cells are starved for energy, your body may begin to break down fat. This produces toxic acids known as ketones. Watch for loss of appetite, weakness, vomiting, fever, stomach pain and a sweet, fruity breath.
You can check your urine for excess ketones with an over-the-counter ketones test kit. If you have excess ketones in your urine, consult your doctor right away or seek emergency care. This condition is more common in people with type 1 diabetes.
Hyperglycemic hyperosmolar nonketotic syndrome. Signs and symptoms of this life-threatening condition include a blood sugar reading over 600 mg/dL (33.3 mmol/L), dry mouth, extreme thirst, fever, drowsiness, confusion, vision loss and hallucinations. Hyperosmolar syndrome is caused by sky-high blood sugar that turns blood thick and syrupy.
It is seen in people with type 2 diabetes, and it's often preceded by an illness. Call your doctor or seek immediate medical care if you have signs or symptoms of this condition.
Low blood sugar (hypoglycemia). If your blood sugar level drops below your target range, it's known as low blood sugar (hypoglycemia). If you're taking medication that lowers your blood sugar, including insulin, your blood sugar level can drop for many reasons, including skipping a meal and getting more physical activity than normal. Low blood sugar also occurs if you take too much insulin or an excess of a glucose-lowering medication that promotes the secretion of insulin by your pancreas.
Check your blood sugar level regularly, and watch for signs and symptoms of low blood sugar — sweating, shakiness, weakness, hunger, dizziness, headache, blurred vision, heart palpitations, irritability, slurred speech, drowsiness, confusion, fainting and seizures. Low blood sugar is treated with quickly absorbed carbohydrates, such as fruit juice or glucose tablets.